Filter arrangement for filtering dust-laden air generated by a hand- guided power tool and power tool arrangement

ABSTRACT

The invention refers to a filter arrangement for filtering dust-laden air (7) generated by a hand-guided power tool (1), in particular a sander or a grinder, during operation of the power tool (1). The filter arrangement comprises a filter cartridge (13) havinga hollow casing (14),a filter element (22) located inside the casing (14),an air inlet port (15) located downstream in respect to an airflow (8) through the filter cartridge (13) and in respect to the filter element (22) and adapted to be pneumatically connected to the power tool (1) in order to allow the dust-laden air (7) generated by the power tool (1) to flow into the casing (14), andan air outlet port (20) located upstream in respect to the airflow (8) through the filter cartridge (13) and in respect to the filter element (22), the air outlet port (20) adapted to allow filtered air (9) leave the filter cartridge (13).It is suggested that the filter arrangement comprises an active airflow generating device (30) with a fan (40) comprising a plurality of blades (44) and driven by an electric motor (38) separate from an electric motor of the power tool (1), the airflow generating device (30) being in pneumatic connection with the air inlet port (15) of the filter cartridge (13) or with the air outlet port (20) of the filter cartridge (13) in order to generate or support the airflow (8) through the filter cartridge (13).

BACKGROUND OF THE INVENTION 1. Field of Invention

The present invention relates to a filter arrangement for filteringdust-laden air generated by a hand-guided power tool having an electricmotor, in particular a sander or a grinder, during operation of thepower tool. The filter arrangement comprises a filter cartridge having

-   -   a hollow casing,    -   at least one filter element located inside the casing,    -   an air inlet port provided in the casing, the air inlet port        located downstream in respect to an airflow through the filter        cartridge and in respect to the filter element, the air inlet        port adapted to be pneumatically connected to the power tool in        order to allow the dust-laden air generated by the power tool to        flow into the casing, and    -   an air outlet port provided in the casing, the air outlet port        located upstream in respect to the airflow through the filter        cartridge and in respect to the filter element, the air outlet        port adapted to allow filtered air leave the filter cartridge.

Further, the invention also relates to a power tool arrangementcomprising a hand-guided power tool, in particular a sander or agrinder, and a filter arrangement for filtering dust-laden air generatedby the power tool during its operation of the above-mentioned kind. Thepower tool could be any electrically or pneumatically driven power toolwhich generates dust during its intended use. Besides the mentionedsanders and grinders, further examples for such power tools are powersaws, power drills, hammer drills, power chisels or the like.

2. Description of Related Art

Filter arrangements of the above-mentioned kind are known in the priorart. For example, RUPES S.p.A. commercializes a filter cartridge underthe name GREENTECH, which may be directly pneumatically connected to anair outlet socket of a hand-guided power tool, in particular a sander.The known filter cartridge is described in detail in EP 1 849 555 A1,which is incorporated herein by reference in its entirety. The powertool comprises a fan which is adapted to blow dust-laden air generatedduring operation of the power tool through the air outlet socket of thepower tool. The filter cartridge is directly pneumatically connected tothe air outlet socket by means of its air inlet port. The filtercartridge constitutes a passive filter arrangement. The air flow ofdust-laden air is generated by the power tool's fan, drawn through thefilter cartridge, thereby filtered and the filtered air is drawn out ofthe filter cartridge into the environment though its air outlet port.The known filter cartridges have small dimensions, are light in weightand have a high degree of flexibility. On the other hand, the airfiltering capabilities and efficiency of the known passive filtercartridges are worthy of improvement.

Furthermore, mobile or stationary vacuum cleaners are known in the art.These can be indirectly pneumatically connected to an air outlet socketof a power tool by means of a suction hose. The vacuum cleaners activelydraw dust-laden air generated by the power tool during its operationinto the vacuum cleaner, where the air is filtered and subsequentlydiscarded into the environment through one or more outlet ports of thevacuum cleaner. Vacuum cleaners have good air filtering capabilities andefficiency. On the other hand, they have rather large dimensions, arerather heavy in weight and have only a limited flexibility. Due to thesize even of mobile vacuum cleaners they cannot be moved, in particularcarried, around easily by a user, in particular they cannot be attachedto a belt of a user looped around the waist of the user or draped over ashoulder of the user. Freedom of movement of the user is significantlyrestricted during use of the power tool with the known vacuum cleaners.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to enhance the airfiltering capabilities and efficiency of known filter arrangements andat the same time to maintain the small dimensions and flexibility offilter cartridges as far as possible.

In order to solve this object, the present invention provides a newfilter arrangement. In particular, starting from the known filterarrangement of the above-mentioned kind, the new filter arrangement mayinclude an active airflow generating device with a fan comprising aplurality of blades and driven by an electric fan motor separate fromthe electric motor of the hand-guided power tool, the airflow generatingdevice being in pneumatic connection with the air inlet port of thefilter cartridge or with the air outlet port of the filter cartridge inorder to generate or support the airflow through the filter cartridge.

According to the present invention the known passive filter cartridgehas been modified in order to turn it into an active filter cartridgewhich actively draws the airflow through the filter cartridge. Theinvention combines the advantages of conventional filter cartridges withthe advantages of conventional vacuum cleaners. The filter arrangementhas very good air filtering capabilities and efficiency of conventionalvacuum cleaners and at the same time maintains the small dimensions andflexibility of conventional filter cartridges. The filter arrangementworks perfectly well with power tools with or without a fan which isadapted to blow dust-laden air generated during operation of the powertool through the air outlet socket of the power tool. It is possible toattach at least part of the filter arrangement to a user's belt loopedaround the waist of the user or draped over a shoulder of the user.Alternatively, it is possible to rigidly attach at least part of thefilter arrangement directly to the power tool so during use of the powertool the directly attached part of the filter arrangement is moved bythe user together with the power tool. Freedom of movement of the useris maintained at a very high level during use of the power tool with thefilter arrangement.

According to a first preferred embodiment of the invention, the airflowgenerating device is in pneumatic connection with the air inlet port ofthe filter cartridge in order to blow the dust-laden air generated bythe power tool through the air inlet port into the casing of the filtercartridge and to create a high pressure inside the casing of the filtercartridge and to blow the filtered air through the air outlet port ofthe filter cartridge, thereby generating or supporting the airflowthrough the filter cartridge. Hence, the airflow generating devicegenerates a low pressure downstream of the air outlet socket of thepower tool thereby conveying the dust-laden air into the filtercartridge. Further, within the filter cartridge the airflow generatingdevice creates a high pressure by blowing the dust-laden air into thefilter cartridge and through at least one filter element located insidethe casing of the filter cartridge. On the other side of the filterelement the filtered air is blown through the air outlet port of thefilter cartridge into the environment. This generates or supports theairflow through the filter cartridge. Additionally, the rotating fangenerates a rotating airflow through the filter cartridge resulting in acyclone or vortex effect hurling larger particles contained in thedust-laden air radially outwards within the filter cartridge. Theparticles hurled radially outwards are collected in the filter cartridgeand will not reach the at least one filter element of the filtercartridge. In this manner, the filter element will have a longerlifetime before clogging with particles. Replacement or cleaning of thefilter element can be performed in much longer intervals. No additionalblades or the like are necessary within the filter cartridge in order togenerate the cyclone or vortex effect. The fan blades are preferablymade of a very robust and hard material, e.g. of steal, possiblyenamelled, ceramics, a synthetic or any compound material.

According to another preferred embodiment of the invention, it issuggested that the airflow generating device is in pneumatic connectionwith the air outlet port of the filter cartridge in order to suck thefiltered air through the air outlet port of the filter cartridge and tocreate a low pressure inside the casing of the filter cartridge therebysucking the dust-laden air generated by the power tool through the airinlet port into the casing of the filter cartridge and generating theairflow through the filter cartridge. The airflow generating device canbe designed and connected to the air outlet port of the filter cartridgesuch that an air stream created by the fan and flowing through theairflow generating device essentially corresponds to the airflow throughthe filter cartridge. Alternatively, the airflow generating device canbe designed and connected to the air outlet port of the filter cartridgesuch that a primary air stream is created by the fan, the primary airstream flowing essentially perpendicular to the airflow through thefilter cartridge in order to generate or support the airflow in themanner of a jet pump. In this embodiment, the air stream generated bythe fan is not the airflow through the filter cartridge.

According to a preferred embodiment of the invention it is suggestedthat the air inlet port of the filter cartridge is directlypneumatically connected to the power tool in order to allow thedust-laden air generated by the power tool to flow directly into thecasing of the filter cartridge. Preferably, the filter cartridge isdirectly connected to an air outlet socket of the hand-guided powertool. The connection is releasable in order to allow detachment of thefilter cartridge from the power tool when desired. The connection can berealized by means of frictional force and/or a bayonet joint between theair outlet socket of the power tool and the air inlet port of the filtercartridge. Any other type of releasable connection between the filtercartridge and the power tool may also be realized. This embodiment hasthe advantage that the power tool and the filter cartridge are rigidlyconnected to each other and constitute a single unit which can be easilyhandled.

Alternatively, it is suggested that the air inlet port of the filtercartridge is indirectly pneumatically connected to the power tool bymeans of a first suction hose in order to make the dust-laden airgenerated by the power tool to flow through the first suction hose intothe casing of the filter cartridge. The suction hose is preferablyconnected to an air outlet socket of the hand-guided power tool with oneend and with its other end to the air inlet port of the filtercartridge. The suction hose is preferably flexible and follows anymovement of the power tool during its operation. The filter cartridgecan be located at any place remote from the power tool. For example, thefilter cartridge could be attached to a belt of a user looped around thewaist of the user or draped over a shoulder of the user. The connectionsof the hose are releasable in order to allow detachment of the hose fromthe power tool and the filter cartridge when desired. The connectionscan be realized by means of frictional force and/or a bayonet jointbetween one end of the suction hose and the air outlet socket of thepower tool and between the other end of the hose and the air inlet portof the filter cartridge. Any other type of releasable connectionsbetween the ends of the suction hose and the filter cartridge and thepower tool, respectively, may also be realized. This embodiment has theadvantage that the hand-guided power tool can be handled and operated toa great extent independently of the filter cartridge. In particular, theweight of the filter cartridge does not have to be moved together withthe power tool during its operation.

According to another preferred embodiment of the invention it issuggested that the airflow generating device is directly pneumaticallyconnected to the air outlet port of the filter cartridge in order toallow the filtered air from the filter cartridge to flow directly intothe airflow generating device. The airflow generating device could bereleasably connected to the air outlet port of the casing of the filtercartridge. The releasable connection could be realized by means offrictional force and/or a bayonet joint. This has the advantage that thecombination of filter cartridge and airflow generating device can bemodularly assembled depending on the individual needs of the respectivefilter arrangement. For example, a filter cartridge with a certain typeof filter element (e.g. a paper filter element, a fabric filter element,a HEPA filter element) or with a certain volume for collecting dust anddebris could be selected and used in the filter arrangement. Further, anairflow generating device for generating a certain flow rate (volume pertime) could be selected and used in the filter arrangement.Alternatively, the airflow generating device could also form an integralpart of that part of the casing of the filter cartridge which comprisesthe air outlet port. This embodiment has the advantage that the filtercartridge and the airflow generating device constitute a single unitwhich can be easily handled. In particular, the single unit comprisingthe filter cartridge and the airflow generating device could be attachedto a belt of a user looped around the waist of the user or draped over ashoulder of the user.

Alternatively, it is suggested that the airflow generating device isindirectly pneumatically connected to the air outlet port of the filtercartridge by means of a second suction hose in order to make thefiltered air from the filter cartridge to flow through the secondsuction hose into the airflow generating device. The suction hose ispreferably connected to the air outlet port of the filter cartridge withone end and with its other end to an air inlet of the airflow generatingdevice. The suction hose is preferably flexible and follows any movementof the filter cartridge and the airflow generating device, respectively,during operation of the power tool and use of the filter arrangement.The airflow generating device can be located at any place remote fromthe filter cartridge and/or the power tool. For example, the airflowgenerating device could be attached to a belt of a user looped aroundthe waist of the user or draped over a shoulder of the user. Theconnections of the hose are releasable in order to allow detachment ofthe hose from the filter cartridge and the airflow generating devicewhen desired. The connections can be realized by means of frictionalforce and/or a bayonet joint between one end of the suction hose and theair outlet port of the filter cartridge and between the other end of thehose and the air inlet of the airflow generating device. Any other typeof releasable connections between the ends of the suction hose and thefilter cartridge and the airflow generating device, respectively, mayalso be realized. This embodiment has the advantage that the hand-guidedpower tool can be handled and operated to a great extent independentlyof the airflow generating device. In particular, the weight of theairflow generating device does not have to be moved together with thepower tool during its operation.

According to another preferred embodiment of the invention it issuggested that the airflow generating device comprises a housing and inthe housing an electric motor and a fan driven by the electric motor,the fan comprising a plurality of blades, and that the housing comprisesan air inlet located downstream in respect to the fan and in respect toan air stream flowing through the airflow generating device during itsoperation and an air outlet located upstream in respect to the fan andin respect to the air stream flowing through the airflow generatingdevice. The fan or its blades, respectively, may be optimized in orderto provide for a particularly efficient (large flow rate per energyconsumption and size and weight, respectively) airflow generatingdevice. Preferably, the blades extend radially outwards from an internalrotor-hub.

According to yet another embodiment of the invention, the airflowgenerating device comprises a housing, and in the housing an electricmotor and at least partly in the housing a battery pack for operatingthe electric motor independently from a mains power supply. Thisembodiment has the advantage that the active filter arrangement worksself-sufficient and independent from any external power supply. Noseparate cables for energy supply of the airflow generating device haveto be provided. This is particularly advantageous if also the power toolwith which the filter arrangement works together with and to which it isattached is also operated by a battery independently from a mains powersupply.

It is suggested that the housing of the airflow generating devicecomprises an externally accessible compartment for receiving at leastpart of the battery pack, and wherein the battery pack is extractablefrom the compartment. The battery pack is electrically contacted withthe electronic components of the airflow generating device automaticallyupon full insertion into the compartment. To this end, the compartmentas well as a housing of the battery pack is provided with electriccontacts which enter into contact upon full insertion of the batterypack into the compartment. The battery pack may be releasably attachedto the housing of the airflow generating device, for example by means ofa spring or snap lock or magnetically. This embodiment has the advantagethat the battery pack can be extracted from the housing, e.g. forcharging a used-up battery pack and/or for replacing a used-up batterypack by another (fully) charged battery pack. This allows an almostinfinite almost continuous use of the active filter arrangement.

According to a preferred embodiment the airflow generating devicecomprises a power supply unit with a cable and a power plug forattachment to a power socket of a mains power supply, the power supplyunit being adapted to be at least partly inserted into the compartmentinstead of the battery pack for operating the electric motor withelectric energy from the mains power supply. The power supply unit iselectrically contacted with the electronic components of the airflowgenerating device automatically upon full insertion into thecompartment. To this end, the compartment as well as a housing of thepower supply unit is provided with electric contacts which enter intocontact upon full insertion of the power supply unit into thecompartment. The power supply unit may be releasably attached to thehousing of the airflow generating device, for example by means of aspring or snap lock or magnetically. The power supply unit comprises allelectric and electrical components necessary for transforming thevoltage of the mains power supply (e.g. 230V or 110V) into an operatingvoltage of the airflow generating device (e.g. 12V, 18V, 24V, 36V, 48V)and possibly also the current of the mains power supply into anoperating current of the airflow generating device. The electric andelectronic components may comprise a transformer, a rectifier, acontroller or regulator, and one or more capacitors, coils, inductances,resistors. This embodiment has the advantage that in case of a long useof the power tool and the filter arrangement or when sanding largeworkpiece surfaces, the filter arrangement can be operated with electricenergy from the mains power supply.

Alternatively, the airflow generating device comprises an adapter unitwith a first cable connected to an external power supply unit with asecond cable and a power plug for attachment of the external powersupply unit to a power socket of a mains power supply, the adapter unitbeing adapted to be at least partly inserted into the compartmentinstead of the battery pack for operating the electric motor withelectric energy from the mains power supply. The adapter unit iselectrically contacted with the electronic components of the airflowgenerating device automatically upon full insertion into thecompartment. To this end, the compartment as well as a housing of theadapter unit is provided with electric contacts which enter into contactupon full insertion of the adapter unit into the compartment. Theadapter unit may be releasably attached to the housing of the airflowgenerating device, for example by means of a spring or snap lock ormagnetically. The adapter unit merely serves as an interface between thecompartment and the power supply unit. The power supply unit comprisesall electric and electrical components necessary for transforming thevoltage of the mains power supply (e.g. from 100V to 240V, from 50 Hz to60 Hz alternate voltage) into an operating voltage of the airflowgenerating device (e.g. 12V, 18V, 24V, 36V, 48V, preferably a directvoltage) and possibly also the current of the mains power supply into anoperating current of the airflow generating device. The electric andelectronic components may comprise a transformer, a rectifier, acontroller or regulator, and one or more capacitors, coils, inductances,resistors. The adapter unit may at the most comprise passive electriccomponents. This embodiment has the advantage that in case of a long useof the power tool and the filter arrangement or when sanding largeworkpiece surfaces, the filter arrangement can be operated with electricenergy from the mains power supply. At the same time, the filterarrangement can be operated without having to carry around the (ratherheavy and bulky) power supply unit. The power supply unit can be putdown and set aside on the floor or any other desired place.

According to yet another preferred embodiment of the present invention,it is suggested that the casing of the filter cartridge comprises a liddetachable from the rest of the casing and comprising the air outletport, wherein the airflow generating device forms an integral part ofthe lid. The lid may be detached from the rest of the casing in order toempty the casing from dust and debris filtered out of the dust-laden airand collected in the casing and/or to remove the filter element forcleaning or replacement by another filter element. Preferably, the lidcomprises the housing, the electric motor and the fan of the airflowgenerating device as an integral part. Hence, the lid and the housing ofthe airflow generating device are a single element. This has theadvantage that the filter cartridge and the airflow generating devicecan be easily handled as a single unit. In particular, the single unitcomprising the filter cartridge and the airflow generating device couldbe attached to a belt of a user looped around the waist of the user ordraped over a shoulder of the user.

The active filter arrangement may work with power tools with or withoutan integrated dust extraction system. The dust extraction systemintegrated in the power tool may comprise a fan adapted for blowing thedust-laden air generated by the power tool through an air outlet socketof the power tool, to which the air inlet port of the filter cartridgeis directly or indirectly pneumatically connected. The fan is driven bya drive shaft of the power tool, which may also drive a backing pad ofthe tool, to which a sanding material is attached. The fan supports theeffect of the airflow generating device. While the airflow generatingdevice sucks the dust-laden air into the filter cartridge, the fan blowsthe dust-laden air into the filter cartridge. Of course, the filterarrangement according to the invention will work just as well inconnection with power tools without an integrated dust extractionsystem.

The object of the invention is also solved by a power tool arrangementcomprising a hand-guided power tool, in particular a sander or agrinder, and a filter arrangement according to the present invention forfiltering dust-laden air generated by the power tool during itsoperation. Preferably, the power tool comprises a transmitter device fortransmitting radio signals containing information relating to operationof the power tool, in particular to turning on and/or turning off thepower tool. These radio signals may be received by a respective receiverdevice making part of the airflow generating device. A processing unitof the airflow generating device may process received signals, extractinformation contained therein, evaluate the extracted information anddepending on the content of the information provide for automaticstart/stop of the electric motor of the airflow generating device.Alternatively, the airflow generating device may be provided with aswitch, preferably easy to actuate, e.g. with working gloves at theuser's hands, by the palm of a user's hand or the user's elbow, in orderto allow an easy manual start/stop of the electric motor of the airflowgenerating device.

Further features and advantages of the present invention will bedescribed in more detail hereinafter with reference to various preferredembodiments shown in the accompanying drawings. The features of thevarious embodiments described and shown in the drawings may be combinedin any desired manner, even if that specific combination is notexplicitly described and/or shown in the drawings. The drawings show:

BRIEF DESCRIPTION OF THE DRAWING

The Drawing includes the following Figures:

FIG. 1 a conventional filter arrangement known in the art;

FIG. 2 a filter arrangement according to a preferred embodiment of theinvention;

FIG. 3 a filter arrangement according to another preferred embodiment ofthe invention;

FIG. 4 a filter arrangement according to yet another preferredembodiment of the invention;

FIG. 5 a preferred embodiment of a filter cartridge of the filterarrangement of FIGS. 2 to 4 ;

FIG. 6 an airflow generating device of the filter arrangement of FIGS. 2and 3 according to a first embodiment;

FIG. 7 an airflow generating device of the filter arrangement of FIGS. 2and 3 according to a second embodiment;

FIG. 8 an airflow generating device of the filter arrangement of FIGS. 2and 3 according to a third embodiment;

FIG. 9 the filter arrangement of FIG. 2 in a schematic view;

FIG. 10 a filter arrangement according to another embodiment of theinvention in a schematic view;

FIG. 11 a filter arrangement according to yet another embodiment of theinvention in a schematic view; and

FIG. 12 a filter arrangement according to yet another embodiment of theinvention in a schematic view.

DETAILED DESCRIPTION OF THE BEST MODE OF THE INVENTION

FIG. 1 shows a conventional filter arrangement like it is known, forinstance, from EP 1 849 555 A1. The filter arrangement serves forfiltering dust-laden air generated by a hand-guided power tool 1 duringits operation. The filter arrangement comprises a filter cartridge 13pneumatically connected to the power tool 1. In the shown embodiment thepower tool 1 is embodied as an orbital sander. Of course, the power tool1 could also be embodied as a grinder, a power saw, a power drill, ahammer drill, a power chisel or the like. A sanding material is attachedto a bottom surface of a backing pad 3 of the power tool 1. In a viewfrom above the backing pad 3 may have a triangular (delta-shaped), roundor rectangular form. In order to perform a working movement of thebacking pad 3 during the intended use of the power tool 1, the backingpad 3 is driven by a drive shaft 4 which is rotatably supported in abody of the power tool 1 by means of bearings 6. The working movement ofthe backing pad 3 may be purely rotational, random orbital, gear drivenor purely orbital. The drive shaft 4 is driven about its longitudinalaxis by means of a pneumatic or electric motor (not shown) locatedinside a housing 2 of the power tool 1.

The power tool 1 comprises an internal dust suction device comprising afan 5 driven by the drive shaft 4. The fan 5 rotates about thelongitudinal axis of the drive shaft 4. The fan 5 has the task ofaspiring dust-laden air 7 from the backing pad 3 (through holes andchannels provided in the backing pad 3) and from a surface to be workedand to blow the dust-laden air 7 towards a connection tube 10. Theconnection tube 10 leads to an air outlet socket 11 of the power tool 1.The filter cartridge 13 is directly attached to the air outlet socket 11with its air inlet port 15. A seal 12 may be provided between the airoutlet socket 11 of the power tool 1 and the air inlet port 15 of thefilter cartridge 13. The filter cartridge 13 is held by way of frictionon the air outlet socket 11.

The filter cartridge 13 comprises a hollow casing 14 preferably made ofplastic material. The casing 14 has an essentially cylindrical form witha longitudinal extension. At least one filter element 22 is locatedinside the casing 14. The filter element 22 has also an essentiallycylindrical form with a smaller diameter than the casing 14. The casing14 and the filter element 22 preferably share the same longitudinalaxis. The filter element 22 separates the internal chamber of the casing14 into two separate partial chambers, a first external essentiallyhollow cylindrical input chamber 23 and a second internal essentiallycylindrical output chamber 26. The only way for dust-laden air 7contained in the first chamber 23 to reach the second chamber 26 isthrough the filter material of the filter element 22. The air inlet port15 leads into a pre-chamber 104 in which a bladed element 100 islocated. The bladed element 100 has a cylindrical portion 101 withperipheral blades 102 radially extending therefrom and a conical headportion 103, the tip of which pointing towards the air inlet port 15.The bladed element 100 or the conical head portion 101, respectively,separates the first input chamber 23 from the second output chamber 26.On its way through the filter cartridge 13 the dust-laden air 7 passesthrough the filter element 22 in order to filter out dust and debris andto create filtered air 9, which subsequently passes through an airoutlet port 20 of the filter cartridge 13 and is discarded into theenvironment. In respect to the flow of dust-laden air 7, the cyclonicair flow 8 and the flow of filtered air 9, the air inlet port 15 islocated downstream and the air outlet port 20 is located upstream of thefilter element 22.

The bladed element 100 or the peripheral blades 102, respectively,induce a rotation of the dust-laden air 7 when passing the peripheralblades 102, thereby creating a vortex of a cyclonic air flow 8 of thedust-laden air 7 in the first external chamber 23. This provokes anextraction and separation of the larger dust and debris particles fromthe dust laden air 7. The extracted and separated particles arecollected in the first chamber 23, in particular at the bottom of thecasing 14. Hence, the larger particles have already been extracted orseparated from the dust-laden air 7 before the cyclonic air flow 8passes through the filter element 22 from the first input chamber 23into the second output chamber 26. Consequently, the filter element 22has to filter out only smaller particles form the dust-laden air 7 andthe cyclonic air flow 8, respectively, and, therefore, has a much longerlifetime before clogging.

The rear part of the casing 14 comprises a lid 16 which is detachablefrom the rest of the casing 14. The lid 16 is releasably attached to therest of the casing 14 by means of frictional force. The lid 16 comprisesthe air outlet port 20. The filter element 22 and the bladed element 100are attached to the lid 16. The lid 16 may be opened in order to discardthe particles of dust and debris collected in the first external chamber23 and the bottom of the casing 14 and/or in order to clean/replace thefilter element 22.

The filter arrangement according to the present invention, a preferredembodiment of which is shown in FIG. 2 , comprises an airflow generatingdevice 30, which is in pneumatic connection with the air outlet port 20of the filter cartridge 13 in order to suck the filtered air 9 throughthe air outlet port 20 of the filter cartridge 13 and to create a lowpressure inside the casing 14, in particular in the second internalchamber 26, of the filter cartridge 13, thereby sucking the dust-ladenair 7 generated by the power tool 1 through the air inlet port 15 intothe casing 14, in particular into the first external chamber 23, of thefilter cartridge 13 and generating or at least supporting the airflow 7,8, 9 through the filter cartridge 13. In this embodiment the airflowgenerating device 30 is designed and connected with its air inlet 34 tothe air outlet port 20 of the filter cartridge 13 such that an airstream created by the fan 40 and flowing through the airflow generatingdevice 30 essentially corresponds to the airflow 8, 9 through the filtercartridge 13. The low pressure is a pressure below atmospheric pressure,i.e. <1.013 mbar, preferably <500 mbar, particularly preferable <300mbar, ideally <200 mbar.

The airflow generating device 30 of FIG. 2 comprises a housing 32preferably made of plastic material. The housing 32 has an air inlet 34and one or more air outlets 36. In this embodiment the air outlets 36are located in side walls of the housing 32. However, they could just aswell be located in a rear wall of the housing 32 opposite to the airoutlet port 20 of the filter cartridge 13 to which the airflowgenerating device 30 is attached. Located inside the housing 32, theairflow generating device 30 comprises an electric motor 38, preferablya brushless motor, particularly preferred a brushless direct current(BLDC)-motor, and at least one fan 40 driven by the electric motor 38.

The fan 40 may be directly driven by a motor shaft 42 or a transmission(not shown) may be functionally located between the motor shaft 42 andthe fan 40. The fan 40 comprises a number of essentially radiallyextending blades 44. The fan 40 is preferably of the radial type causingair 9 sucked in through the air inlet 34 to be discarded out of thehousing 32 in a radial direction, i.e. perpendicular to a rotationalaxis 46 about which the fan 40 rotates. However, the fan 40 could justas well be of the axial type causing air 9 sucked in to flow through thefan 40 in an axial direction, i.e. parallel to the rotational axis 46(see FIGS. 3 and 4 ).

The electric motor 38 is operated by means of electric energy from amains power supply. The electric energy is transmitted to the motor 38by means of a power cable 48 fixedly attached to the housing 32.Separated wires 50 of the cable 48 are connected to the electric motor38.

The airflow generating device 30 may further comprise a printed circuitboard (PCB; not shown) and/or a control unit (not shown) for controllingoperation of the electric motor 38. The control unit and other electricand/or electronic components of the airflow generating device 30 couldbe attached to the PCB and electrically connected to conductive pathsprovided on the PCB. The control unit may comprise a microprocessoradapted for executing a computer program which realizes the controlunit's control function when executed on the microprocessor. Otherelectric and/or electronic components provided inside the airflowgenerating device 30 may be, for example, a transformer for transforminga voltage in the range of 100 V to 240 V, 50 Hz to 60 Hz, from the mainspower supply into an operation voltage of the airflow generating device30, e.g. a direct voltage in the range of 12 V to 48 V.

Furthermore, the airflow generating device 30 could comprise a switch(not shown) for manually turning on and off the electric motor 38.Preferably, the airflow generating device 30 is provided with a receiverdevice 52 for receiving radio signals 54. The receiver device 52 ispreferably located inside the housing 32 and attached and electricallyconnected to a PCB. A control unit may control operation of the electricmotor 38 depending on the received radio signals 54. The radio signals54 contain information regarding an operation of the power tool 1. Tothis end, the power tool 1 preferably comprises a transmitter device 56which transmits the radio signals 54. The radio signals 54 and theformat of the information contained therein preferably fulfil aBluetooth standard, in particular a Bluetooth low-energy (BLE) standard.The transmitter device 56 is preferably located inside the housing 2 ofthe power tool 1.

When the power tool 1 is activated by the user, e.g. by pressing anON-button or by activating a switch of the power tool 1, a respectiveradio signal 54 is automatically generated and transmitted by thetransmitter device 56 of the power tool 1. The radio signal 54 isreceived by the receiver device 52 of the airflow generating device 30and processed, e.g. by the control unit. As a result of the receptionand/or processing of the radio signal 54, the electric motor 38 isautomatically turned on and the filter arrangement starts filteringdust-laden air 7.

When the power tool 1 is turned off by the user, e.g. by pressing anOFF-button or by activating a switch of the power tool 1, a respectiveradio signal 54 is automatically generated and transmitted by thetransmitter device 56 of the power tool 1. The radio signal 54 isreceived by the receiver device 52 of the airflow generating device 30and processed, e.g. by the control unit. As a result of the receptionand/or processing of the radio signal 54, the electric motor 38 isautomatically turned off and the filter arrangement stops filteringdust-laden air 7. It is possible, to keep the electric motor 38 stillturned on for a certain amount of time after reception and/or processingof the radio signal 54 in order to provide for some kind ofpost-filtering-operation after deactivating the power tool 1.

In contrast to the embodiment of the filter arrangement shown in FIG. 2, the following modifications may be made without departing from theinvention:

-   -   The form of the casing 14 of the filter cartridge 13 may be any        form other than cylindrical, e.g. it may have a square,        rectangular or polygon (e.g. elliptical) form in a cross section        perpendicular to the longitudinal extension of the casing 14.        Consequently, also the form of the first and second chambers 23,        26 may have another form than shown in FIG. 2 .    -   The form of the filter element 22 may be any form other than        cylindrical, e.g. flat.    -   The filter cartridge 13 may have more than one filter element        22.    -   The bladed element 100 for creating the vortex of dust-laden air        8 may be omitted (see the embodiment of FIG. 5 ). In FIG. 5 the        first external chamber 23 is pneumatically separated from the        second internal chamber 26 by wall elements comprising part of        the air outlet port 20 and a separating wall 25 located opposite        the air outlet port 20.

In an alternative embodiment of FIG. 3 , the airflow generating device30 is in pneumatic connection with the air inlet port 15 of the filtercartridge 13 in order to blow the dust-laden air 7 generated by thepower tool 1 through the air inlet port 15 into the casing of the filtercartridge 13 and to create a high pressure inside the casing 14 of thefilter cartridge 13. The filtered air 9 is blown through the air outletport 20 of the filter cartridge 13, thereby generating or supporting theairflow 8 through the filter cartridge 13.

The fan 40 of the airflow generating device 30 of FIG. 3 is preferablyof the axial type causing air 7 sucked in to flow through the fan 40 inan axial direction, i.e. parallel to the rotational axis 46. The airinlet 34 of the airflow generating device 30 is directly connected tothe air outlet socket 11 of the power tool 1. Similarly, the air outlet36 of the airflow generating device 30 is directly connected to the airinlet port 15 of the filter cartridge 13. Of course, it would also bepossible to connected at least some of the devices 11, 30, 13 indirectlyby means of suction hoses or the like.

The rotating fan 40 generates a rotating airflow 8 through the filtercartridge 13 resulting in a cyclone or vortex effect hurling largerparticles contained in the dust-laden air 7 radially outwards within thefilter cartridge 13. The particles hurled radially outwards arecollected in the filter cartridge 13 and will not reach the filterelement 22 of the filter cartridge 13. In this manner, the filterelement 22 will have a longer lifetime before clogging with particlesand replacement or cleaning of the filter element 13 can be performed inlonger intervals. No additional peripheral blades 102 or the like arenecessary within the filter cartridge 13 for generating the cyclone orvortex effect. The fan blades 44 are preferably made of a robust andhard material, e.g. of steal, possibly enamelled, ceramics, a syntheticor any compound material.

In yet another embodiment of FIG. 4 , the airflow generating device 30is in pneumatic connection with the air outlet port 20 of the filtercartridge 13 in order to suck the filtered air 9 through the air outletport 20 of the filter cartridge 13 and to create a low pressure insidethe casing 14 of the filter cartridge 13 thereby sucking the dust-ladenair 7 generated by the power tool 1 through the air inlet port 15 intothe casing 14 of the filter cartridge 13 and generating the airflow 8through the filter cartridge 13. The airflow generating device 30 isdesigned and connected with its air inlet 34 to the air outlet port 20of the filter cartridge 13 such that a primary air stream 17 is createdby the fan 40, the primary air stream 17 flowing essentiallyperpendicular to the airflow 8, 9 through the filter cartridge 13 inorder to generate or support the airflow 8, 9 in the manner of a jetpump. In particular, the primary air stream 17 flows essentiallyperpendicular to the airflow 8, 9 in a region 19 where a tube or chamberfor the airflow 9 merges into a tube or chamber for the primary airstream 17. In this embodiment, the air stream 17 generated by the fan 40is not the airflow 8, 9 through the filter cartridge 13.

Hereinafter, some preferred embodiments of the airflow generating device30 are explained in further detail with reference to FIGS. 6 to 8 . Inthe embodiment of FIG. 6 the airflow generating device 30 is operated byelectric energy from a battery pack 60. To this end, the housing 32comprises an externally accessible compartment 62, into which at leastpart of the battery pack 60 is inserted. The battery pack 60 isreleasably attached to the housing 32 in order to avoid itsunintentional separation and falling out of the compartment 62.Electronic contacts 64 are provided inside the compartment 62 forautomatically effecting an electric connection to respective contacts ofthe battery pack 60 upon complete insertion of the battery pack 60 intothe compartment 62. The battery pack 60 comprises an external casing andone or more battery cells located therein, preferably of theLithium-Ion-type or of the Lithium-Polymer-type. The battery pack 60provides an operating voltage in the range of 12 V to 48 V for theairflow generating device 30.

In the embodiment of FIG. 7 , the battery pack 60 has been released fromthe housing 32 and extracted from the compartment 62. Instead of thebattery pack 60 a power supply unit 66 has been at least partiallyinserted into the compartment 62 and its contacts are in electricconnection with the electric contacts 64 provided in the compartment 62.The power supply unit 66 is releasably attached to the housing 32 inorder to avoid its unintentional separation and falling out of thecompartment 62. The power supply unit 66 has an external casingessentially corresponding to the external casing of the battery pack 60.In particular, at least that part of the power supply unit 66 to beinserted into the compartment 62 corresponds to that part of the batterypack 60 to be inserted into the compartment 62. The form of that part ofthe power supply unit 66 not to be inserted into the compartment 62 maydiffer from the form of that part of the battery pack 60 not to beinserted into the compartment 62.

Preferably, the power supply unit 66 comprises a printed circuit board(PCB) 68 provided in the external casing. Attached and electricallyconnected to the PCB 68 is a transformer 70 for transforming a voltagein the range of 100 V to 240 V, 50 Hz to 60 Hz, from the mains powersupply into an operation voltage of the airflow generating device 30,e.g. a direct voltage in the range of 12 V to 48 V. Attached to the PCB68 there may be further electric and/or electronic components 72comprising, for example, a rectifier, a controller or regulator, and oneor more capacitors, coils, inductances, resistors.

The electric energy of the mains power supply is transmitted to thepower supply unit 66 by means of a power cable 74 fixedly attached tothe external casing of the power supply unit 66. Separate wires 76 ofthe cable 74 are connected to the PCB 68. The power cable 74 is providedwith a plug 78 at its distal end for connection to a mains power supplysocket. This embodiment has the advantage that the airflow generatingdevice 30 can be operated for an almost infinite amount of time. Duringoperation of the airflow generating device 30 with the power supply unit66 the battery pack 60 may be recharged in an external charging station(not shown).

In the embodiment of FIG. 8 , the battery pack 60 has been released fromthe housing 32 and extracted from the compartment 62. Instead of thebattery pack 60 an adapter unit 80 has been at least partially insertedinto the compartment 62 and its contacts are in electric connection withthe electric contacts 64 provided in the compartment 62. The adapterunit 80 is releasably attached to the housing 32 in order to avoid itsunintentional separation and falling out of the compartment 62. Theadapter unit 80 has an external casing essentially corresponding to theexternal casing of the battery pack 60. In particular, at least thatpart of the adapter unit 80 to be inserted into the compartment 62corresponds to that part of the battery pack 60 to be inserted into thecompartment 62. The form of that part of the adapter unit 80 not to beinserted into the compartment 62 may differ from the form of that partof the battery pack 60 not to be inserted into the compartment 62.

The adapter unit 80 is provided with a first cable 82 connected to anexternal power supply unit 84. The external power supply unit 84 isprovided with a second cable 86 and a power plug 88 at its distal endfor connection of the external power supply unit 84 to a power socket(not shown) of a mains power supply. Preferably, the adapter unit 80merely serves as an interface between the power supply unit 84 and thecontacts 64 of the compartment 62. To this end, separate wires 83 of thefirst cable 82 are connected to the contacts of the adapter unit 80adapted for entering into contact with the contacts 64 of thecompartment 62 upon complete insertion of the adapter unit 80 into thecompartment 62.

Preferably, the power supply unit 84 has an external casing andcomprises a printed circuit board (PCB) 90 provided in the externalcasing. Attached and electrically connected to the PCB 90 is atransformer 92 for transforming a voltage in the range of 100 V to 240V, 50 Hz to 60 Hz, from the mains power supply into an operation voltageof the airflow generating device 30, e.g. a direct voltage in the rangeof 12 V to 48 V. Attached to the PCB 90 there may be further electricand/or electronic components 94 comprising, for example, a rectifier, acontroller or regulator, and one or more capacitors, coils, inductances,resistors. Separate wires 96 of the second cable 86 are connected to thePCB 90. These wires 96 convey the electric energy from the mains powersupply to the transformer 92 and preferably comprise three wires 96, onefor the phase conductor (with black or brown isolation), one for theneutral conductor (with blue or grey isolation) and one for theprotective conductor (with green/yellow isolation). Further, separatewires 98 of the first cable 82 are connected to the PCB 90. These wires98 convey the electric energy for the operation of the airflowgenerating device 30, which was previously transformed by thetransformer 92. They preferably comprise two wires 98, one for thepositive voltage (with red isolation) and one for the negative voltage(with black isolation).

Besides the various ways of realization of the airflow generating device30, there are various further possibilities how the filter arrangementaccording to the present invention may be realized. Schematic views ofpossible realizations are shown in FIGS. 9 to 12 .

The embodiment shown in FIG. 9 essentially corresponds to the embodimentof FIG. 2 . The filter cartridge 13 is directly attached with its airinlet port 15 to the air outlet socket 11 of the power tool 1. Thefilter cartridge 13 is releasably connected to the power tool 1. Thedirect connection between the air outlet socket 11 of the power tool 1on the one hand and the air inlet port 15 of the filter cartridge 13 onthe other hand is realized by means of frictional force, a bayonet jointand/or a snap connection. Alternatively, the direct connection couldalso be embodied my means of magnetic force. Further, the airflowgenerating device 30 is directly attached to the air outlet port 20 ofthe filter cartridge 13. In the case of a releasable connection betweenthe filter cartridge 13 and the airflow generating device 30, the directconnection between the air outlet port 20 of the filter cartridge 13 andthe airflow generating device 30 is realized by means of frictionalforce, a bayonet joint and/or a snap connection. The releasable directconnection could also be embodied my means of magnetic force.Alternatively, the airflow generating device 30 could also form anintegral part of a part of the casing 14 of the filter cartridge 13comprising the air outlet port 20. In particular, the airflow generatingdevice 30 could form an integral part of the lid 16. The lid 16 may bereleasably attached to the rest of the casing 14 by means of frictionalforce, a bayonet joint and/or a snap connection. The releasableattachment could also be embodied my means of magnetic force.

FIG. 10 shows another embodiment of the filter arrangement. In contrastto the embodiment of FIG. 7 , the airflow generating device 30 isindirectly attached to the air outlet port 20 of the filter cartridge 13by means of a second suction hose 106. One end of the hose 106 isconnected to the air outlet port 20 of the filter cartridge 13 and theother end of the hose 106 is connected to an air inlet 34 (see FIGS. 2and 6 to 8 ) of the airflow generating device 30. The suction hose 106is preferably releasably connected to the filter cartridge 13 and theairflow generating device 30. The releasable connection between thesuction hose 106 and the filter cartridge 13 on the one hand and/or thesuction hose 106 and the airflow generating device 30 on the other handmay be realized by means of frictional force, a bayonet joint or a snapconnection. The releasable connection could also be embodied my means ofmagnetic force. In this embodiment, the airflow generating device 30 maybe attached to a belt 110 looped around the waist of the user or drapedover a shoulder of the user (see FIGS. 10 to 12 ). The power tool 1 andthe filter cartridge 13 are rigidly connected to each other andconstitute a single unit which can be easily handled. Hence, thisembodiment provides for a maximum amount of freedom of movement for theuser during use of the power tool 1 without having to carry theadditional weight of the airflow generating device 30 at the power tool1 during its use.

FIG. 11 shows yet another embodiment of the filter arrangement. Incontrast to the embodiment of FIG. 10 , the filter cartridge 13 isindirectly attached to the air outlet socket 11 of the power tool 1 bymeans of a first suction hose 108. One end of the hose 108 is connectedto the air outlet socket 11 of the power tool 1 and the other end of thehose 108 is connected to the air inlet port 15 of the filter cartridge13. The suction hose 108 is preferably releasably connected to the powertool 1 and the filter cartridge 13. The releasable connection betweenthe suction hose 108 and the power tool 1 on the one hand and/or betweenthe suction hose 108 and the filter cartridge 13 on the other hand maybe realized by means of frictional force, a bayonet joint or a snapconnection. The releasable connection could also be embodied my means ofmagnetic force. In this embodiment, the filter cartridge 13 and/or theairflow generating device 30 may be attached to a belt 110 looped aroundthe waist of the user or draped over a shoulder of the user. Hence, thisembodiment provides for a maximum amount of freedom of movement for theuser during use of the power tool 1 without having to carry theadditional weight of the filter cartridge 13 and the airflow generatingdevice 30 at the power tool 1 during its use.

Finally, FIG. 12 shows yet another embodiment of the present invention.In contrast to the embodiment of FIG. 11 , the airflow generating device30 is directly attached to the filter cartridge 13, similar theembodiments of FIGS. 2 and 9 . The airflow generating device 30 may bereleasably attached to the filter cartridge 13 or it may form anintegral part of at least part of the casing 14 of the filter cartridge13, e.g. of the lid 16. In this embodiment, the filter cartridge 13 andthe airflow generating device 30 are rigidly connected to each other andconstitute a single unit which can be easily handled. In particular, theunit may be attached to a belt 110 looped around the waist of the useror draped over a shoulder of the user. Hence, this embodiment providesfor a maximum amount of freedom of movement for the user during use ofthe power tool 1 without having to carry the additional weight of thefilter cartridge 13 and the airflow generating device 30 at the powertool 1 during its use.

The invention claimed is:
 1. Filter arrangement for filtering dust-ladenair (7) generated by a hand-guided power tool (1) having an electricmotor, including a sander or a grinder, during operation of thehand-guided power tool (1), the filter arrangement comprising a filtercartridge (13) having a hollow casing (14), at least one filter element(22) located inside the hollow casing (14), an air inlet port (15)provided in the hollow casing (14), the air inlet port (15) locatedupstream with respect to an airflow (8) through the filter cartridge(13) and with respect to the at least one filter element (22), the airinlet port (15) adapted to be pneumatically connected to the hand-guidedpower tool (1) in order to allow the dust-laden air (7) generated by thehand-guided power tool (1) to flow into the hollow casing (14), and anair outlet port (20) provided in the hollow casing (14), the air outletport (20) located downstream with respect to the airflow (8) through thefilter cartridge (13) and with respect to the at least one filterelement (22), the air outlet port (20) adapted to allow filtered air (9)to leave the filter cartridge (13); the filter arrangement having anactive airflow generating device (30) with a fan (40) comprising aplurality of blades (44) and driven by an electric fan motor (38)separate from the electric motor of the hand-guided power tool (1), theairflow generating device (30) being in pneumatic connection with theair inlet port (15) of the filter cartridge (13) in order to generate orsupport the airflow (8) through the filter cartridge (13); wherein theairflow generating device (30) is in pneumatic connection with the airinlet port (15) of the filter cartridge (13) in order to blow thedust-laden air (7) generated by the hand-guided power tool (1) throughthe air inlet port (15) into the hollow casing (14) of the filtercartridge (13) and to create a pressure higher than the ambient pressureinside the hollow casing (14) of the filter cartridge (13) and to blowthe filtered air (9) through the air outlet port (20) of the filtercartridge (13), thereby generating or supporting the airflow (8) throughthe filter cartridge (13).
 2. Filter arrangement according to claim 1,wherein the airflow generating device (30) is a portable device adaptedto be carried by a user of the filter arrangement.
 3. Filter arrangementaccording to claim 1, wherein the airflow generating device (30)comprises a housing (32) having the electric fan motor (38) arrangedtherein, and also having a battery pack (60) arranged at least partlytherein for operating the electric fan motor (38) independently from amains power supply.
 4. Filter arrangement according to claim 3, whereinthe housing (32) of the airflow generating device (30) comprises anexternally accessible compartment (62) for receiving at least part ofthe battery pack (60), and wherein the battery pack (60) is extractablefrom the externally accessible compartment (62).
 5. Filter arrangementaccording to claim 1, wherein the airflow generating device (30)comprises a power supply unit (66) with a cable (74) and a power plug(78) for attachment to a power socket of a mains power supply, and alsocomprises an externally accessible compartment (62) for receiving atleast part of the power supply unit (66) for operating the electric fanmotor (38) with electric energy from the mains power supply.
 6. Filterarrangement according to claim 1, wherein the airflow generating device(30) comprises an adapter unit (80) with a first cable (82) connected toan external power supply unit (84) with a second cable (86) and a powerplug (88) for attachment of the external power supply unit (84) to apower socket of a mains power supply, and also comprises an externallyaccessible compartment (62) for receiving at least part of the adapterunit (80) for operating the electric fan motor (38) with electric energyfrom the mains power supply.
 7. Filter arrangement according to claim 1,wherein the airflow generating device (30) comprises a receiver device(52) for receiving radio signals (54) containing information relating tooperation of the hand-guided power tool (1), and wherein the airflowgenerating device (30) is automatically activated or deactivateddepending on a content of the radio signals (54) received.
 8. Power toolarrangement comprising the hand-guided power tool (1), and the filterarrangement for filtering dust-laden air (7) generated by thehand-guided power tool (1) during its operation, wherein the filterarrangement is configured according to claim
 1. 9. Power toolarrangement according to claim 8, wherein the hand-guided power tool (1)comprises a transmitter device (56) for transmitting radio signals (54)containing information relating to operation of the hand-guided powertool (1), including turning on and/or turning off the hand-guided powertool (1).
 10. Filter arrangement according to claim 2, wherein theairflow generating device (30) is attached to a belt looped around thewaist of a user or draped over a shoulder of the user.
 11. Filterarrangement for filtering dust-laden air (7) generated by a hand-guidedpower tool (1) having an electric motor, including a sander or agrinder, during operation of the hand-guided power tool (1), the filterarrangement comprising a filter cartridge (13) having a hollow casing(14), at least one filter element (22) located inside the hollow casing(14), an air inlet port (15) provided in the hollow casing (14), the airinlet port (15) located upstream with respect to an airflow (8) throughthe filter cartridge (13) and with respect to the at least one filterelement (22), the air inlet port (15) adapted to be pneumaticallyconnected to the hand-guided power tool (1) in order to allow thedust-laden air (7) generated by the hand-guided power tool (1) to flowinto the hollow casing (14), and an air outlet port (20) provided in thehollow casing (14), the air outlet port (20) located downstream withrespect to the airflow (8) through the filter cartridge (13) and withrespect to the at least one filter element (22), the air outlet port(20) adapted to allow filtered air (9) to leave the filter cartridge(13); the filter arrangement having an active airflow generating device(30) with a fan (40) comprising a plurality of blades (44) and driven byan electric fan motor (38) separate from the electric motor of thehand-guided power tool (1), the airflow generating device (30) being inpneumatic connection with the air inlet port (15) of the filtercartridge (13) in order to generate or support the airflow (8) throughthe filter cartridge (13); wherein the airflow generating device (30) isin pneumatic connection with the air outlet port (20) of the filtercartridge (13) in order to suck the filtered air (9) through the airoutlet port (20) of the filter cartridge (13) and to create a pressurelower than the ambient pressure inside the hollow casing (14) of thefilter cartridge (13) thereby sucking the dust-laden air (7) generatedby the hand-guided power tool (1) through the air inlet port (15) intothe hollow casing (14) of the filter cartridge (13) and generating orsupporting the airflow (8) through the filter cartridge (13); andwherein the airflow generating device (30) is indirectly pneumaticallyconnected to the air outlet port (20) of the filter cartridge (13) by asecond suction hose (106) in order to make the filtered air (9) from thefilter cartridge (13) flow through the second suction hose (106) intothe airflow generating device (30).
 12. Filter arrangement according toclaim 11, wherein the air inlet port (15) of the filter cartridge (13)is directly pneumatically connected to the hand-guided power tool (1) inorder to allow the dust-laden air (7) generated by the hand-guided powertool (1) to flow directly into the hollow casing (14) of the filtercartridge (13).
 13. Filter arrangement according to claim 11, whereinthe air inlet port (15) of the filter cartridge (13) is indirectlypneumatically connected to the hand-guided power tool (1) by a firstsuction hose (108) in order to make the dust-laden air (7) generated bythe hand-guided power tool (1) flow through the first suction hose (108)into the hollow casing (14) of the filter cartridge (13).
 14. Filterarrangement according to claim 11, wherein the airflow generating device(30) is directly pneumatically connected to the air outlet port (20) ofthe filter cartridge (13) in order to allow the filtered air (9) fromthe filter cartridge (13) to flow directly into the airflow generatingdevice (30).
 15. Filter arrangement according to claim 12, wherein theairflow generating device (30) is directly pneumatically connected tothe air outlet port (20) of the filter cartridge (13) in order to allowthe filtered air (9) from the filter cartridge (13) to flow directlyinto the airflow generating device (30).
 16. Filter arrangement forfiltering dust-laden air (7) generated by a hand-guided power tool (1)having an electric motor, including a sander or a grinder, duringoperation of the hand-guided power tool (1), the filter arrangementcomprising a filter cartridge (13) having a hollow casing (14), at leastone filter element (22) located inside the hollow casing (14), an airinlet port (15) provided in the hollow casing (14), the air inlet port(15) located upstream with respect to an airflow (8) through the filtercartridge (13) and with respect to the at least one filter element (22),the air inlet port (15) adapted to be pneumatically connected to thehand-guided power tool (1) in order to allow the dust-laden air (7)generated by the hand-guided power tool (1) to flow into the hollowcasing (14), and an air outlet port (20) provided in the hollow casing(14), the air outlet port (20) located downstream with respect to theairflow (8) through the filter cartridge (13) and with respect to the atleast one filter element (22), the air outlet port (20) adapted to allowfiltered air (9) to leave the filter cartridge (13); wherein the filterarrangement comprises an active airflow generating device (30) with afan (40) comprising a plurality of blades (44) and driven by an electricfan motor (38) separate from the electric motor of the hand-guided powertool (1), the airflow generating device (30) being in pneumaticconnection with the air inlet port (15) of the filter cartridge (13) inorder to generate or support the airflow (8) through the filtercartridge (13), wherein the airflow generating device (30) comprises ahousing (32) having the electric fan motor (38) and the fan (40)arranged therein, having an air inlet (34) located upstream with inrespect to the fan (40) and with respect to an air stream flowingthrough the airflow generating device (30) upon its activation, and alsohaving an air outlet (36) located downstream with respect to the fan(40) and with respect to the air stream flowing through the airflowgenerating device (30); and wherein the air stream is a primary airstream flowing perpendicular to the airflow (8) through the filtercartridge (13) in order to generate or support the airflow (8) in themanner of a jet pump.
 17. Filter arrangement for filtering dust-ladenair (7) generated by a hand-guided power tool (1) having an electricmotor, including a sander or a grinder, during operation of thehand-guided power tool (1), the filter arrangement comprising a filtercartridge (13) having a hollow casing (14), at least one filter element(22) located inside the hollow casing (14), an air inlet port (15)provided in the hollow casing (14), the air inlet port (15) locateddownstream with respect to an airflow (8) through the filter cartridge(13) and with respect to the at least one filter element (22), the airinlet port (15) adapted to be pneumatically connected to the hand-guidedpower tool (1) in order to allow the dust-laden air (7) generated by thehand-guided power tool (1) to flow into the hollow casing (14), and anair outlet port (20) provided in the hollow casing (14), the air outletport (20) located upstream with respect to the airflow (8) through thefilter cartridge (13) and with respect to the at least one filterelement (22), the air outlet port (20) adapted to allow filtered air (9)to leave the filter cartridge (13), the filter arrangement having anactive airflow generating device (30) with a fan (40) comprising aplurality of blades (44) and driven by an electric fan motor (38)separate from the electric motor of the hand-guided power tool (1), theairflow generating device (30) being in pneumatic connection with theair inlet port (15) of the filter cartridge (13) in order to generate orsupport the airflow (8) through the filter cartridge (13); and whereinthe hollow casing (14) of the filter cartridge (13) comprises a lid (16)detachable from the rest of the hollow casing (14) and comprising theair outlet port (20), wherein the airflow generating device (30) formsan integral part of the lid (16).
 18. Filter arrangement for filteringdust-laden air (7) generated by a hand-guided power tool (1) having anelectric motor, including a sander or a grinder, during operation of thehand-guided power tool (1), the filter arrangement comprising a filtercartridge (13) having a hollow casing (14), at least one filter element(22) located inside the hollow casing (14), an air inlet port (15)provided in the hollow casing (14), the air inlet port (15) locatedupstream with respect to an airflow (8) through the filter cartridge(13) and with respect to the at least one filter element (22), the airinlet port (15) adapted to be pneumatically connected to the hand-guidedpower tool (1) in order to allow the dust-laden air (7) generated by thehand-guided power tool (1) to flow into the hollow casing (14), and anair outlet port (20) provided in the hollow casing (14), the air outletport (20) located downstream with respect to the airflow (8) through thefilter cartridge (13) and with respect to the at least one filterelement (22), the air outlet port (20) adapted to allow filtered air (9)to leave the filter cartridge (13); the filter arrangement having anactive airflow generating device (30) with a fan (40) comprising aplurality of blades (44) and driven by an electric fan motor (38)separate from the electric motor of the hand-guided power tool (1), theairflow generating device (30) being in pneumatic connection with theair inlet port (15) of the filter cartridge (13) in order to generate orsupport the airflow (8) through the filter cartridge (13); wherein theairflow generating device (30) is in pneumatic connection with the airoutlet port (20) of the filter cartridge (13) in order to suck thefiltered air (9) through the air outlet port (20) of the filtercartridge (13) and to create a pressure lower than the ambient pressureinside the hollow casing (14) of the filter cartridge (13) therebysucking the dust-laden air (7) generated by the hand-guided power tool(1) through the air inlet port (15) into the hollow casing (14) of thefilter cartridge (13) and generating or supporting the airflow (8)through the filter cartridge (13); wherein the air inlet port (15) ofthe filter cartridge (13) is directly pneumatically connected to thehand-guided power tool (1) in order to allow the dust-laden air (7)generated by the hand-guided power tool (1) to flow directly into thehollow casing (14) of the filter cartridge (13); and wherein the airflowgenerating device (30) is indirectly pneumatically connected to the airoutlet port (20) of the filter cartridge (13) by a second suction hose(106) in order to make the filtered air (9) from the filter cartridge(13) flow through the second suction hose (106) into the airflowgenerating device (30).